OF THE DEPENDEÎs^T ISLES OF TAIWAN. bO 



THE ISLE OF KASHO (SA3IASANA). 



(Fl III, Fig. G.) 



Kasho is a forest- covered, conical volcanic island {J^'ig. 1), 

 only 8 km. in circumference, skirted by fringing reefs. The 

 inhabitants are of the mixed blood of the Chinese and the 

 Malays. According to Mr. Ishii, who gave me a rock-specimen, 

 the island is Andesitic, consisting of Pumice and. lava-flows, and 

 carries two craters. My slide show^s the rock to be the Hypei^s- 

 thene-hornblende- Andésite. 



To the naked eye the rock resembles very closely those of 

 Héradaké, in Shinano, and Hakusan in the Kaga province. It 

 is greyish-looking, with the only pheiiocryst of hornblende, 

 measuring 5 mm. by 2. The hornblende is the largest of 

 phenocrysts (on the right half of Fig. ö), broad-columnar in 

 form in combination of 110 and 010, and has always thick 

 margin of opacité. The hornblende has dark-brown colour, and 

 optically normal. It encloses the grains of felspar after the 

 fashion of poikilitic plate, especially on periphery. This fact 

 conclusively shows the simultaneous crystallisation of the 

 hornblende in its later period with the forerunner of plagioclase. 

 The formation of these crystals might have taken place at the 

 close of intratelluric period, of the magma. The opacitic margin 

 consists, as usual, of the grains of monoclinic pyroxene and 

 magnetite. They seem to have been formed by resorption and 

 re-combination through the gradual caustic action of the surround- 

 ing magma upon the already existing hornblende, at a slightly 

 lower pressure and in the upper column of effusive lava than 

 the situation in which the original amphibole has crystallized 

 out. The majority of crystals seems to have been eaten up by 



